1. Department of Mathematics, COMSATS University Islamabad, Wah Campus, Wah Cantt, Pakistan
2. School of Electrical Engineering and Computer Science (SEECS), National University of Sciences and Technology (NUST), Sector H-12, Islamabad, Pakistan
3. Department of Mathematics, College of Science, King Saud University, P.O. Box 22452, Riyadh 11495, Saudi Arabia
4. Faculty of Science and Technology, University of the Faroe Islands, Torshavn, Faroe Islands
5. Department of Mathematics, University of the Gambia, Serrekunda, The Gambia